It is known that the genetic information of each living creature, its genome, is contained in its chromosomes, which are made up of long chains of nucleic acids, namely DNA and RNA.
All these nucleic acids are therefore constituted by a chaining of nucleotides having either a purine base (adenine or guanine) or a pyrimidine base (cytosine or uracil in RNA and cytosine or thymine in DNA).
Point-by-point analysis of polynucleotides deposited on a substrate is considered to be a promising tool for analysis of the shape of each successive purine or pyrimidine base. Shape reconstruction and identification of said bases can be envisaged. But problems, including control of the method of arranging and localizing polynucleotides on a substrate for accurate analysis of the successive bases thereof, still have to be solved.
One attempt at such a method is described by LEE et al in SCIENCE, vol 244 (1989) pp 475-477.
According to this reference, bundles of molecules are deposited freely in droplets on a substrate and a scanning tunnel effect microscope is used to image tertiary (helical) DNA structure.